Means and method for automatically controlling the hydrogen to hydrocarbon mole ratio during the conversion of a hydrocarbon

ABSTRACT

In a hydrocarbon converting unit in a petroleum refinery, the hydrogen to hydrocarbon mole ratio is controlled in accordance with the following equation: WHERE VH is the volume percent hydrogen in recycle gas, Gg is the specific gravity of the recycle gas, Fg is the flow rate of the recycle gas, Gc is the specific gravity of charge oil, Fc is the charge oil flow rate, Mc is the average molecular weight of the charge oil and the term 13261.21 is a conversion factor. Signal means sample the charge oil and the recycle gas and provide signals corresponding to the specific gravity of the charge oil Gc and of the recycle gas Gg, the average molecular weight Mc of the charge oil and the quantity of hydrogen VH in the recycle gas. Flow transmitters sense the flow rates Fc and Fg of the charge oil and the recycle gas, respectively, and provide corresponding signals. An analog computer computes the hydrogen to hydrocarbon mole ratio in accordance with the aforementioned equation and the signals from the signal means and the flow transmitters and provides an output corresponding thereto. An error signal is developed using an output from the analog computer and a reference signal corresponding to a desired value for the hydrogen to hydrocarbon mole ratio. The error signal is used to control the hydrogen entering the hydrocarbon converting unit so as to maintain the hydrogen to hydrocarbon mole ratio at the desired value.

ilitd t s Hopkins et a1.

Primary ExaminerJoseph F. Ruggiero Attorney-Thomas H. Whaley and Carl G.Ries [57] ABSTRACT In a hydrocarbon converting unit in a petroleum 1Inventors! W l Llopkins, Houston; refinery, the hydrogen to hydrocarbonmole ratio is 118m Nederland, both of controlled in accordance with thefollowing equation: Tex.; Luther F. Champion, Cherry Hill,N.J. C VHGQFUGF V [73] Assignee: Texaco Development Corporation, 13261.21 X i NewYork, N.Y. c [22] Filed; May 30 2 where V is the volume percent hydrogenin recycle gas, G, is the specific gravity of the recycle gas, F is [2]]pp N 257,644 the flow rate of the recycle gas, G is the specific gravityof charge oil, P is the charge oil flow rate, M, Related Apphcatlon Datais the average molecular weight of the charge oil and [63] Continuationof Ser. No. 97,571, Dec. 14, 1970, the term 13261.21 is a conversionfactor. Signal abandoned. means sample the charge oil and the recyclegas and provide signals corresponding to the specific gravity of [52][1.8. C1. ..235/l51.12,23/255 E, 208/134, the charge oil G and of therecycle gas G the /D1G. 1 average molecular weight M of the charge oiland the [51] Int. Cl ..C10g 35/04,G06g 7/58 quantity of hydrogen V inthe recycle gas. Flow [58] Field Of Search ..235/151.12, 151.1,transmitters sense the flow rates P and F of the 235/150, 150.1, 151.3,151.34, 151.35; charge oil and the recycle gas, respectively, and pro-208/134, 138, 139, DIG. 1; 196/132; 23/230 vide corresponding signals.An analog computer com- R, 232 R, 252 R, 254 E, 255 E putes the hydrogento hydrocarbon mole ratio in accordance with the aforementioned equationand the signals from the signal means and the flow transmitters [56]References Cited and provides an output corresponding thereto. An errorsignal is developed using an output from the UNITED STATES PATENTSanalog coriirTu'tei'an d a reference signal corresponding 3,497,449 21970 Urban ..235/151.12X to a desired value for the hydrogen tohydrocarbon 3,213,014 10/1965 Atkinson et a1. ..208/DIG.1 mole ratio.The error signal is used to control the 3,520,800 7/ 1970 Forbes..208/138 X hydrogen entering the hydrocarbon converting unit so3,539,784 11/1970 Woodie ..235/151.l2 as to maintain the hydrogen tohydrocarbon H1016 3,540,996 1 1/1970 Maziuk .208/138 X ratio at thedesired value.

8 l m QW ns ews l E DIVIDER VIDER SPEED FLOW V answer :03 2e i E il 95 ImSE T EU iilTENT E -En} VOLTAGE I 02 1 E27 2a FLOW 1 2! 22 TRANSMITTERMULTPL'ER E l o s '05 B94 i/ zo q SIGNAL 4 CLOCK A (80 MEANS 20 i 87 17MULTIPLIER 5 i i STEAM 2 M I I 126 CAT REACTOR SIGNAL FLOW 15 MEANS 2GAS PRODUCT 24 76 CHARGE OIL P ODUCT SEPARATOR LIQUID PRODUCT 1 MEANSAND METHOD FOR AUTOMATICALLY CONTROLLING THE HYDROGEN TO HYDROCARBONMOLE RATIO DURING THE CONVERSION OF A HYDROCARBON CROSS REFERENCE TORELATED APPLICATIONS This application is a continuation as to allsubject matter common to US. application Ser. No. 97,571 filed Dec. 14,1970, and now abandoned, by Walker L. Hopkins, William D. White andLuther F. Champion and assigned to Texaco Inc., assignee of the presentinvention, and a continuation-in-part for all additional subject matter.

BACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates to controlling hydrocarbon converting units and, moreparticularly, to controlling the hydrogen to hydrocarbon mole ratioduring the hydrocarbon conversion.

2. Description of the Prior Art Previously, control of the hydrogen tohydrocarbon mole ratio of a catalytic reforming operation in an oilrefinery was done manually. An article appearing in the Oil and GasJournal, Volume 58, No. 13 on Mar. 28, 1960 and entitled ComputerControl of Catalytic Reforming Processes by Mr. Reuben Silver, statedthat catalytic reforming could be controlled by a computer and mentionsthat the hydrogen to hydrocarbon mole ratio was a variable in thecatalytic reforming operation. However, the subject article did notdisclose the apparatus for automatically controlling the hydrogen tohydrocarbon mole ratio. Furthermore, it is not obvious to one skilled inthe art in reading the article how the hydrogen to hydrocarbon moleratio may be automatically controlled.

The device of the present invention monitors some of the operatingparameters of a hydrocarbon converting operation, such as catalyticreforming, and regulates the recycle gas flow in accordance with themonitored parameters to provide automatic control of the hydrogen tohydrocarbon mole ratio.

SUMMARY OF THE INVENTION A system for controlling the hydrogen tohydrocarbon mole ratio of a mixture in a hydrocarbon converting unit inwhich the hydrogen and the hydrocarbon entering the hydrocarbonconverting unit are sensed and corresponding signals are provided. Asignal corresponding to the hydrogen to hydrocarbon ratio is developedin accordance with the hydrogen and the hydrocarbon signals. A circuitprovides an error signal corresponding to the difference between theratio signal and a reference signal corresponding to a predeterminedhydrogen to hydrocarbon mole ratio. The error signal is used to controlone of the entrants to the hydrocarbon converting unit.

One object of the present invention is to automatically control thehydrogen to hydrocarbon mole ratio during the conversion of hydrocarbon.

Another object of the present invention is to control the hydrogen tohydrocarbon mole ratio during the conversion of the hydrocarbon inaccordance with the equation Another object of the present invention isto automatically control the hydrogen to hydrocarbon mole ratio in anoperating hydrocarbon converting unit in accordance with sensedquantities of charge oil and gas entering the hydrocarbon convertingunit so that said control is substantially instantaneous.

Another object of the present invention is to improve the economy of thehydrocarbon converting operation by maintaining the hydrogen tohydrocarbon mole ratio at a predetermined optimum value.

The foregoing and other objects and advantages of the invention willappear more fully hereinafter from a consideration of the detaileddescription which follows, taken together with the accompanying drawingswherein one embodiment of the invention is illustrated by way ofexample. It is to be expressly understood, however, that the drawingsare for illustration purposes only and are not to be construed asdefining the limits of the invention.

DESCRIPTION OF THE DRAWINGS FIG. 1 shows a block diagram of a system,constructed in accordance with the present invention, for controllingthe hydrogen to hydrocarbon mole ratio during the catalytic reformingoperation in a refinery.

FIGS. 2 and 3 are detailed block diagrams of the two signal means shownin FIG. 1.

DESCRIPTION OF THE INVENTION During catalytic reforming processing ofoil, gas containing hydrogen is recycled from a product separator to thecatalytic reforming reactor. The gas is used to reduce the rate of cokeformation on the catalyst in the catalytic reforming reactor to retardthe reduction in effectiveness of the catalyst due to the cokeformation. The recycling of the gas requires the use of steam powerwhich represents an economic cost, the rate of flow of the oil in theprocess represents another economic cost, and the effectiveness of thecatalyst represents yet another economic cost.

It is not practical for the recycle gas to have a constant rate sincethe charge oils molecular weight, composition and flow rate as well asthe composition of the gas may vary. An important facet of the processis to control the hydrogen to hydrocarbon mole ratio as a function ofthe aforementioned economic costs. The hydrogen to hydrocarbon moleratio controls the buildup of coke on the catalyst.

Referring to FIG. 1, charge oil enters a catalytic reactor 5 by way of aline 6 while recycle gas enters line 6 by way of a line 7. The reformatefrom reactor 5 enters a product separator 10 where it is separated intogas, part of which is discharged through a line 15, and into a liquidwhich is discharged through a line 16. A portion of the gas in line 14is fed back to reactor 5 as recy cle gas by a compressor 17 driven by asteam motivated turbine 20. The hydrogen to hydrocarbon mole ratio iscontrolled by controlling the steam being applied to turbine 20 therebycontrolling the amount of hydrogen entering reactor 5, as hereinafterexplained.

When activated to the on position, an on-off switch 22 passes samplingpulse from a clock 21 to signal means 24, 87 for controlling signalmeans 24, 87 to provide for the operation of the device of the presentinvention, as hereinafter explained. Switch 22 blocks the samplingpulses from clock 21 when in the off position.

Signal means 24 samples the charge oil in line 6 and provides signal E Ecorresponding to the average molecular weight M and the specific gravityG respectively, of the sample charge oil in accordance with directcurrent voltages E through E from a source 25 of direct currentvoltages, and the following equations:

where -u 2 X: 100.60783 .ooieooustm) .45u xo%) (3) G (l4l.5/API+l3l.5)(6) where 50 percent is the ASTM 50 percent boiling point in F, and APIis the API gravity at 60F.

Signal means 24, shown in detail in FIG. 2, includes analyzers 28, 29which provide signals E and E corresponding to the boiling point and theAPI gravity of the charge oil. The effluent from analyzers 28, 29 may bereturned to line 6 or disposed of as slop.

Analyzer 28 may be a boiling point analyzer of the type manufactured bythe Technical Oil Tool Corporation as their model 6500. Analyzer 29 is aDynatol density analyzer. A suitable analyzer for the density analysisis the series 3006 manufactured by the Automation Products, Inc. andwhich is temperature compensated so that signal E corresponds to the APIgravity at 60F.

Signal E from analyzer 28 is applied to a conventional type sample andhold circuit 34 which is controlled by the sampling pulses passed byswitch 22. The output from sample and hold circuit 34 is summed withdirect current calibration voltage E, by summing means 35 to provide asignal E corresponding to the 50 percent boiling point.

A signal E corresponding to Z in the equation 5 is developed by amultiplier 38 andsubtracting means 40. Multiplier 38 multiplies signalE; with direct current voltage E corresponding to the term 0.516() inequation 5 to provide a product signal to summing means 40. Subtractingmeans 40 subtracts direct voltage E corresponding to the term .0133 inequation 5 from the product signal to provide signal E A signal Ecorresponding to X in equation 3 is developed by multipliers 43, 44 and45, summing means 48, 49 and an antilog circuit 50. Multiplier 43multiplies the 50 percent boiling point signal E, with direct currentvoltage E corresponding to the coefficient .0016007 in equation 3, toprovide a product signal to summing means 48 where it is summed withdirect current voltage E corresponding to the term 1.60783 in equation3. Multiplier 44 in effect squares signal E and provides a correspondingsignal to multiplier 45. Multiplier 45 multiplies the signal frommultiplier 44 with direct negative current voltage E corresponding tothe term .45( 10) in equation 3, to provide a signal. Summing means 49sums the signal from multiplier 45 with the signal from summing means48. Antilog circuit 50 provides signal E in accordance with the sumsignal from summing means 49. Antilog circuits 50, 59 are operationalamplifiers, each having a function generator type feedback element,which may be of the PC-l2 type manufactured by Electronics Associates.

A signal E corresponding to Y in equation 4 is devel oped by multipliers54, 55 and 56, summing means 58, and antilog circuit 59. Signal E fromantilog circuit 50 is multiplied with direct current voltage Ecorresponding to the coefficient .00152 in equation 4, by multiplier 56to provide a corresponding signal. Signal E is effectively squared bymultiplier 54 and the resulting signal is multiplied with direct currentvoltage E corresponding to the coefficient .45 X 10 in equation 4, bymultiplier 55 to provide a corresponding signal. Antilog circuit 59provides signal E in accordance with a sum signal from summing means 58relating to the summation of the signals from multipliers 55, 56 andnegative direct current voltage E, corresponding to the term -.4244 inequation 4.

A conventional type circuit 63 samples and holds signal E, from analyzer29. The output from hold circuit 63 has direct current voltage Ecorresponding to term 30 in equation 2, subtracted from it bysubtracting means 64. The output from subtracting means 64 is squared bya multiplier 68 and the resulting signal is multiplied with signal E,from subtracting means 40 by a multiplier 69. The output fromsubtracting means 64 is also multiplied with signal E from antilogcircuit 59 by a multiplier 70. Outputs from multipliers 69, 70 andsignal E, from antilog circuit 50 are summed by summing means 72 toprovide signal E Signal E is developed by converting signal Ecorresponding to the API gravity at 60 to specific gravity G inaccordance with equation 6.

Signal E, has direct current voltage E corresponding to the term 131.5in equation 6, added to it by summing means 75. A divider 78 dividesdirect current voltage E corresponding to the term 141.5 in equation 6,by the output from adding means 75 to provide signal E Referring againto FIG. 1, conventional types sensing means 75 and flow transmitter 76cooperate to provide a signal E corresponding to the flow rate of thecharge oil in line 6. Signals E E are multiplied by a multiplier 80 toprovide a product signal to a divider 81. Divider 81 divides the productsignal from multiplier 80 with signal E from signal means 24 to providea signal E corresponding to the term F G /M in equation 1.

Signal means 87 provides signals E E corresponding to the percent volumeof hydrogen V,, in the recycle gas and to the specific gravity G, of therecycle gas, respectively. Signal means 87 is shown in detail in FIG. 3.Chromatographic means 88 which includes a chromatograph that may be ofthe type manufactured by Beckman Instruments with a Beckman model 620programmer and a Beckman model D analyzer, providing signals E through Ecorresponding to the hydrogen, methane, ethane, propane, normal butane,isobutane, normal pentane, isopentane, and the hexanes and heavierconstituents, respectively, of the recycle gas. Sample and hold circuits90 through 90H periodically sample and hold signals E through E inresponse to the sampling pulses from switch 22 to provide signals Ethrough E respectively. The specific gravity of the recycle gas isdetermined in accordance with the following equation:

molecular weight of Signals E through E are applied to multipliers 94through 941-1, respectively, where they are multiplied with a directcurrent voltage E corresponding to 0.01 to provide product signals. Theproduct signals from multipliers 94 through 941-1 are multiplied withdirect current voltages E through E respectively, by multipliers 95through 95H. The product signals from multipliers 95 through 95Hcorrespond to the molecular weights of hydrogen, methane, ethane,propane, normal butane, isobutane, normal pentane, isopentane and thehexanes constituents, respectively, and are summed by summing means 99to provide a sum signal. The sum signal from summing means 99 is dividedby direct current voltage E corresponding to the term 29 in equation 6,by a divider 100 to provide specific gravity signal E20.

Referring to FIGv 1, signals E E are multiplied with each other by amultiplier 102 to provide a product signal, corresponding to the productV G, to a multiplier 103. A conventional type sensing element 104 and aflow transmitter 105, which may also be of a conventional type, sensesthe flow rate F, of the recycle gas and provides a corresponding signalE to multiplier 103 where signal E is multiplied with the signal frommultiplier 102 to provide a signal E corresponding to product V G,,F,,of equation 1. Signal B is divided by signal E from divider 81 by adivider 110 to provide an output to an amplifier 1 12 having a gaincorresponding to l/ 13261.21. Although an amplifier is used, amultiplier for multiplying the output from divider 110 with a directcurrent voltage corresponding to l/ l326l.2l may also be used. Theoutput from amplifier 112 corresponds to the actual hydrogen tohydrocarbon-mole ratio.

Source 25 provides a variable amplitude direct current reference voltageE,, which corresponds to a desired hydrogen to hydrocarbon mole ratiosuch as the current economical optimum hydrogen to hydrocarbon moleratio. Ratio controller 116 provides an output signal to a conventionaltype speed controller 120, in accordance with output from amplifier 112and voltage E to change its set point accordingly. Speed controller 120also receives a signal E from a tachometer 121 corresponding to therotational speed of turbine 20. Speed controller 120 acts as a safetydevice to prevent turbine 20 from exceeding its speed limitation. Whenthe speed of turbine 20 differs from the set point speed of speedcontroller 120, speed controller 120 provides a signal to flow recordercontroller 125 receiving a signal E which corresponds to the flow rateof the steam to turbine 20, from a sensing element 126. The signal fromspeed controller 120 adjusts the set point of flow recorder controller125. Flow recorder controller 125 provides a pneumatic control signal toa valve 130 corresponding to the difference between the signal fromsensing element 126 and the set point to control the flow of the steamthereby controlling the flow rate of the recycle gas.

The device of the present invention was heretofore described in terms ofanalog computing elements. It would be obvious to one skilled in the artto use a digital computer to control the hydrogen to hydrocarbon moleratio. Analog signals E E E E E and E are converted to digital signalsby conventional type analog-todigital converters. The digital computeris programmed to solve the aforementioned equations, using the digitalsignals, to provide a digital output corresponding to the differencebetween the actual hydrogen to hydrocarbon mole ratio and the targethydrogen to hydrocarbon mole ratio. The digital output is converted toan analog signal by a conventional type digital-to-analog converter,which is applied to speed controller 120.

Although a hydrogen to hydrocarbon mole ratio control system for acatalytic reforming unit has been disclosed, the control system may alsobe used for the hydrogenation of middle distillates (kerosine and lightgas oils). If the charge oil is lube oil, which requires processing by ahyfinishing unit, signal means 24 would have to be modified to provide asignal corresponding to the molecular weight of the lube oil. However,the overall control concept would not change.

The device of the present invention as heretofore describedautomatically maintains the hydrogen to hydrocarbon mole ratio during ahydrocarbon converting operation in accordance with the equationdisclosed in the abstract and a desired hydrogen to hydrocarbon moleratio. The device of the present invention economically controls thehydrogen to hydrocarbon mole ratio in an operating catalytic reformingunit in accordance with a predetermined optimum value using sensedconditions of charge oil and gas entering the catalytic reforming unitso that said control is substairtially instantaneous.

What is claimed is:

1. A system for controlling the hydrogen to hydrocarbon mole ratioduring the operation of a hydrocarbon converting unit, comprising meansfor sensing the flow rate F of the hydrocarbon and providing acorresponding signal, a pair of meters receiving some of thehydrocarbon, one meter providing a signal corresponding to the boilingpoint of the hydrocarbon: the other meter providing a signalcorresponding to the API gravity of the hydrocarbon, means connected tothe one meter for converting the signal from the one meter to a signalcorresponding to the 50 percent boiling point of the hydrocarbon,computing means connected to the other meter and to the converting meansfor providing signal corresponding to the specific gravity G and theaverage molecular weight M of the hydrocarbon in accordance with theoutput from the other meter and from the converting means and thefollowing equations:

G (141.5/API 131.5)

M X Y(API30) Z(API-3O) where API is the API gravity, means for sensinghydrogen entering the hydrocarbon converting unit and providingcorresponding signals, means connected to the computing means and to thehydrocarbon sensing means for providing a ratio signal corresponding tothe hydrogen to hydrocarbon mole ratio in accordance with the signalsfrom the hydrogen sensing means and the computing means, means forproviding a reference signal corresponding to a predetermined hydrogento hydrocarbon mole ratio, means connected to the ratio signal means andto the reference signal means for providing a signal corresponding tothe difference between the ratio signal and the reference signal, andmeans connected to the signal difference means for controlling one ofthe entrants to the hydrocarbon converting unit in accordance with thesignal so as to control the hydrogen to hydrocarbon mole ratio.

2. A system as described in claim 1 in which the controlled entrant isthe hydrogen and is a constituent of a gas entering the hydrocarbonconverting unit.

3. A system as described in claim 2 in which the hydrogen sensing meansincludes means connected to the ratio signal means for sensing the flowrate F of the gas containing the hydrogen and providing a correspondingsignal to the ratio signal means, chromatographic means for sampling thegas and providing signals corresponding to the percent volumes ofdifferent constituents of the gas, means connected to the chromatographmeans and to the ratio signal means for conducting the signalcorresponding to the percent volume of hydrogen V in the gas from thechromatographic means to the ratio signal means, and first computingmeans connected to the chromatographic means and to the ratio signal forproviding a signal corresponding to the specific gravity G, of the gasin accordance with the signals volume percent of constituent i'of thegas 100 G (l4l.5/API+131.5)

where API is the API gravity, providing a signal corresponding to theaverage molecular weight M of the hydrocarbon in accordance with the APIgravity signal, the 50 percent boiling point and the followingequations:

determining the ratio of hydrogen to hydrocarbon in accordance with thesensed hydrogen signals, the hydrocarbon flow rate F signal and thehydrocarbon specific gravity G and molecular weight M signals; providinga reference signal corresponding to a predetermined hydrogen tohydrocarbon mole ratio, providing an error signal corresponding to thedifference between the ratio signal and the reference signal; andcontrolling the quantity of one of the entrants to the hydrocarbonconverting unit in accordance with the error signal.

6. A method as described in claim 5 in which the controlled entrant isthe hydrogen and the hydrogen is a constituent of a gas entering thehydrocarbon convertmolecular wt. of constituent 2' 4. A system asdescribed in claim 3 in which the ratio signal means provides the ratiosignal in accordance with the signal from the hydrocarbon flow ratesensing means, the gas flow rate sensing means and the first and secondcomputing means and the following equation:

G F 13261.21 X 1W0 and M is the average molecular weight of thehydrocarbon.

5. A method for controlling the hydrogen to hydrocarbon mole ratio in ahydrocarbon converting unit, which comprises providing signalscorresponding to hydrogen entering the hydrocarbon converting unit,sensing the flow rate F of hydrocarbon entering the hydrocarbonconverting unit, providing a signal corresponding to the sensedhydrocarbon flow rate F sensing the boiling point of the hydrocarbon,providing a signal corresponding to the 50 percent boiling point inaccordance with the sensed boiling point, sensing the API gravity of thehydrocarbon, providing a signal corresponding to the sensed API gravity,providing a signal corresponding to the specific gravity G of thehydrocarbon in accordance with the API gravity signal in the followingequation:

ing unit.

7. A method as described in claim 6 in which the step of providingsignals corresponding to the hydrogen entering the hydrocarbonconverting unit includes sensing the flow rate F of the gas containingthe hydrogen, providing a signal corresponding to the sensed flow rateF, of the gas, sensing the percent volume of different constituents ofthe gas, providing a signal corresponding to the sensed percent volume Vof hydrogen in the gas, providing signals corresponding to the percentvolumes of the other constituents of the gas, providing a signalcorresponding to the specific gravity G, of the gas in accordance withthe constituents signals and the following equation:

volume percent of constituent z' of the g a s if molecular wt.

of constituent 1;

8. A device adapted to receive oil and to receive voltages for providingsignals substantially corresponding to the molecular weight and to thespecific gravity of the oil, comprising means for sensing the 50 percentboiling point and the API gravity of the received oil and providingsignals thereto, a pair of sample and hold circuits, connected to thesensing means and controlled by a received voltage, one sample and holdcircuit periodically samples and holds the signal from the sensing meanscorresponding to the 50 percent boiling point of the oil to provide anoutput, while the other sample and hold circuit periodically samples andholds the signal from the sensing means corresponding to API gravity ofthe oil to provide an output, and a computing network connected to thepair of sample and hold circuits for providing the signal substantiallycorresponding to the molecular weight M, of the received oil inaccordance with the outputs from the sample and hold cir- 9 10 cuits,some of the received voltages and the following other sample and holdcircuit for a signal correspondequations: ing to the specific gravity Gof the oil in accordance M X Y(API-30) Z (API30) with the outputcorresponding to the API gravity from .Ol33 .0OO516(50%) 5 the othersample and hold circuit, some of the received X deovsa.oo1eoo1(so%)-.4suoxmf) voltages and the following equation:

and

G (141.5/API+131.5).

where API is the API gravity of the received oil, and 50 10 percent isthe 50 percent boiling point of the received oil; and a second computingnetwork connected to the where API is the API gravity of thehydrocarbon.

1. A system for controlling the hydrogen to hydrocarbon mole ratioduring the operation of a hydrocarbon converting unit, comprising meansfor sensing the flow rate Fc of the hydrocarbon and providing acorresponding signal, a pair of meters receiving some of thehydrocarbon, one meter providing a signal corresponding to the boilingpoint of the hydrocarbon, the other meter providing a signalcorresponding to the API gravity of the hydrocarbon, means connected tothe one meter for converting the signal from the one meter to a signalcorresponding to the 50 percent boiling point of the hydrocarbon,computing means connected to the other meter and to the converting meansfor providing signal corresponding to the specific gravity Gc and theaverage molecular weight Mc of the hydrocarbon in accordance with theoutput from the other meter and from the converting means and thefollowing equations: Gc (141.5/API + 131.5) Mc X + Y(API30) +Z(API-30)2, X 10(1.60783 .0016007(50%BP) .45(10 )(50%BP) ) Y 10( .4244.00152X .45 )X) , Z -.0133+.516(10 4)(50% BP), where API is the APIgravity, means for sensing hydrogen entering the hydrocarbon convertingunit and providing corresponding signals, means connected to thecomputing means and to the hydrocarbon sensing means for providing aratio signal corresponding to the hydrogen to hydrocarbon mole ratio inaccordance with the signals from the hydrogen sensing means and thecomputing means, means for providing a reference signal corresponding toa predetermined hydrogen to hydrocarbon mole ratio, means connected tothe ratio signal means and to the reference signal means for providing asignal corresponding to the difference between the ratio signal and thereference signal, and means connected to the signal difference means forcontrolling one of the entrants to the hydrocarbon converting unit inaccordance with the signal so as to control the hydrogen to hydrocarbonmole ratio.
 2. A system as described in claim 1 in which the controlledentrant is the hydrogen and is a constituent of a gas entering thehydrocarbon converting unit.
 3. A system as described in claim 2 inwhich the hydrogen sensing means includes means connected to the ratiosignal means for sensing the flow rate Fg of the gas containing thehydrogen and providing a corresponDing signal to the ratio signal means,chromatographic means for sampling the gas and providing signalscorresponding to the percent volumes of different constituents of thegas, means connected to the chromatograph means and to the ratio signalmeans for conducting the signal corresponding to the percent volume ofhydrogen VH in the gas from the chromatographic means to the ratiosignal means, and first computing means connected to the chromatographicmeans and to the ratio signal for providing a signal corresponding tothe specific gravity Gg of the gas in accordance with the signals fromthe chromatographic means and the following equation:
 4. A system asdescribed in claim 3 in which the ratio signal means provides the ratiosignal in accordance with the signal from the hydrocarbon flow ratesensing means, the gas flow rate sensing means and the first and secondcomputing means and the following equation: where VH is the percentagevolume of hydrogen in the gas, Gg is the specific gravity of the gas, Fgis the rate of flow of the gas, Gc is the specific gravity of thehydrocarbon, Fc is the rate of flow of the hydrocarbon, and Mc is theaverage molecular weight of the hydrocarbon.
 5. A method for controllingthe hydrogen to hydrocarbon mole ratio in a hydrocarbon converting unit,which comprises providing signals corresponding to hydrogen entering thehydrocarbon converting unit, sensing the flow rate Fc of hydrocarbonentering the hydrocarbon converting unit, providing a signalcorresponding to the sensed hydrocarbon flow rate Fc, sensing theboiling point of the hydrocarbon, providing a signal corresponding tothe 50 percent boiling point in accordance with the sensed boilingpoint, sensing the API gravity of the hydrocarbon, providing a signalcorresponding to the sensed API gravity, providing a signalcorresponding to the specific gravity Gc of the hydrocarbon inaccordance with the API gravity signal in the following equation: Gc(141.5/API+131.5) where API is the API gravity, providing a signalcorresponding to the average molecular weight Mc of the hydrocarbon inaccordance with the API gravity signal, the 50 percent boiling point andthe following equations: Mc X + Y(API-30)+Z(API-30)2 , X 10(1.60783.0016007(50%) .45(10 )(50%) ) , Y 10( .4244 .00152X .45(10 )X ) , Z.0133+.516(10 4)(50%) determining the ratio of hydrogen to hydrocarbonin accordance with the sensed hydrogen signals, the hydrocarbon flowrate Fc signal and the hydrocarbon specific gravity Gc and molecularweight Mc signals; providing a reference signal corresponding to apredetermined hydrogen to hydrocarbon mole ratio, providing an errorsignal corresponding to the difference between the ratio signal and thereference signal; and controlling the quantity of one of the entrants tothe hydrocarbon converting unit in accordance with the error signal. 6.A method as described in claim 5 in which the controlled entrant is thehydrogen and the hydrogen is a constituent of a gas entering thehydrocarbon converting unit.
 7. A method as described in claim 6 inwhich the step of providing signals corresponding to the hydrogenentering the hydrocarbon converting unit includes sensing the flow rateFg of the gas containing the hydrogen, providing a signal correspondingto the sensed flow rate Fg of the gas, sensing the percent volume ofdifferent constituents of the gas, providing a signal corresponding tothe sensed percent volume VH of hydrOgen in the gas, providing signalscorresponding to the percent volumes of the other constituents of thegas, providing a signal corresponding to the specific gravity Gg of thegas in accordance with the constituents signals and the followingequation:
 8. A device adapted to receive oil and to receive voltages forproviding signals substantially corresponding to the molecular weightand to the specific gravity of the oil, comprising means for sensing the50 percent boiling point and the API gravity of the received oil andproviding signals thereto, a pair of sample and hold circuits, connectedto the sensing means and controlled by a received voltage, one sampleand hold circuit periodically samples and holds the signal from thesensing means corresponding to the 50 percent boiling point of the oilto provide an output, while the other sample and hold circuitperiodically samples and holds the signal from the sensing meanscorresponding to API gravity of the oil to provide an output, and acomputing network connected to the pair of sample and hold circuits forproviding the signal substantially corresponding to the molecular weightMc of the received oil in accordance with the outputs from the sampleand hold circuits, some of the received voltages and the followingequations: Mc X + Y(API-30) + Z(API-30)2 Z -.0133 + .0000516(50%) X10(1.60783 .0016007(50%) .45(10 )(50%) ), and Y 10( .4244 .00152X .45(10)X ) where API is the API gravity of the received oil, and 50 percent isthe 50 percent boiling point of the received oil; and a second computingnetwork connected to the other sample and hold circuit for a signalcorresponding to the specific gravity Gc of the oil in accordance withthe output corresponding to the API gravity from the other sample andhold circuit, some of the received voltages and the following equation:Gc (141.5/API+131.5) . where API is the API gravity of the hydrocarbon.